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Aroma Science

The Basics of Essential Oils

As the interest in aromatherapy grows for those interested in alternative health, wellness, and fitness, many folks ask “what are essential oils?” and “how do they differ from other oils like olive oil, coconut and the like?” This brief primer should help clarify the matter, and get you started in the wonderful world of aromatherapy.

What Are Essential Oils?

Essential oils are concentrated volatile aromatic compounds produced by plants – the easily evaporated essences that give plants their wonderful scents – more akin to an alcohol than what we commonly think of as oil. Each of these complex precious liquids is extracted from a particular plant species, originating from various regions around the world, reflecting the unique environmental conditions and neighboring fauna and flora present in these areas. The result is a very diverse library of aromatic compounds, with some essential oils being made up of more than one hundred distinct organic chemicals.

Pure essential oils are distilled from oil sacs found in most structures of the plant – the leaves, roots, flowers, etc. Almost all essential oils are made up of several, sometimes hundreds, of various molecular compounds. The combination and ratios of these compounds give each oil its unique aromatic and therapeutic properties. Essential oils are not just a by-product of plant growth, however. Plants use these oils to fight infections from microbes, fungi, and viruses; to protect themselves from animal invaders, and some suspect they may even be used for chemical communication between plants of the same species. While essential oils come from the plant world, they are particularly suited to use in natural health, wellness, and fitness programs, as their chemistry is remarkably compatible with our own, as they can be easily absorbed into our bodies (even at the cellular level).

The Plants Behind the Oils

The odoriferous substances (essential oils) themselves are formed in the chloroplasts of the leaves, where they combine with glucose to form glucides, and are then circulated around the plant in this form. At certain times of the day or year, these oils are stored in particular parts of the plant. In some plants, the essential oils are produced by the secretory tissues, and in others, they are combined with glycosides, and are therefore not detectable until the plant is dried or crushed (e.g. Valerian).

Essential oils are considered to be an important part of the plant’s metabolism: some have hormonal activity, while others are just a stage in some other process of the plant (e.g. the oil found in the rind of the orange is a stage in Vitamin A synthesis).

Essential oils can be found in almost any part of the plant, in differing concentrations, depending on the plant itself, as well as the time of day/year. They may be found in the roots (e.g. Calamus and Valerian), the flowers (Lavender, Rose), the bark (Sandalwood, Cedarwood), the fruits (Lemon, Cardamom, Orange), the berries (Juniper), or the leaves (Thyme, Rosemary, Sage).

Plants which contain essences must be picked at the correct time of day and in the correct season, and in weather conditions that will produce the maximum yield of essential oils that can be obtained. Of course, as with all medicinal or nutritional plants, soil and climatic conditions will also dictate the quality of the oils that can be obtained.

The Process Of Distillation

There are several distillation processes through which essential oils are extracted from aromatic plants. Steam-distillation and water-distillation are two of the main methods, among many others (of these two, the steam process is more popular). Many are of the view that steam is the only true way to extract essential oils for aromatherapy. (Read More Here)


The aromatic vapors condense into liquid upon cooling. This mixture of oil and water (oil from condensed aromatic vapors, water from condensed steam) is collected in another vessel. As is the nature of oil and water, they separate automatically upon cooling, with the oil at the top and water at the bottom. The oil from the top is then simply siphoned off. The result is a highly-concentrated oil that can be used in aromatherapy.


For the water distillation process, a still is also used. In this instance, the aromatic plant is placed in the still and sunken in water. The water is boiled, which helps release the aromatic molecules and oils of the plant, in the same way as steam distillation. The aromatic vapors are cooled and then easily separated from the water. This method of extraction is appropriate for plants that cannot withstand high temperatures and pressures.

Steam and Water-Distillation

Another method of distillation is the combination of steam and water. In this process, the aromatic plant is placed in a still and submerged under water. Steam is then introduced to help release the aromatic molecules and oils of the plant. Upon cooling, the essential oils are collected and separated, as explained above.

The aromatic oils extracted by the above methods produce essential oils in their concentrated forms. In case of topical aromatherapy, these oils should never be applied to the skin in their concentrated forms. They are diluted with the help of carrier oils, such as Almond, Hazelnut or Olive.

Determining Quality

Producing essential oils of the highest-grade is truly an art form. It takes a delicate balance of time, temperature, and pressure during the distillation process to ensure the complete range of molecular components is extracted. The finest oils will have the most wonderful aromatic bouquets for this reason – they contain a breadth of compounds that, when inhaled together, give an oil a brilliant aroma. However, relatively few essential oils are produced in this manner. Many are destined for large manufacturing processes, and will not have the same aromas and therapeutic effects of the highest-grade oils. (Read More Here)

History of Essential Oils

Medicinal and spiritual use of essential oils dates back thousands of years. Oils were used by the ancient Egyptians along with many other ancient cultures; there are hundreds of references to their healing properties in the Christian Bible, along with anointing for spiritual growth and insight. Frankincense resin continues to be used in the Catholic church today during mass as a purifying and uplifting aromatic incense – a similar application of essential oils can be the anointing of the third eye or temples with Frankincense, Myrrh, Cedarwood, Sandalwood or a combination of these mind-centering aromatics. (Read More Here)

Contemporary Use

Modern use of essential oils in natural health, wellness and fitness programs began with the discovery of Lavender‘s healing properties by a French scientist in the middle of the last century. Lavender was found to have effective healing properties for skin wounds, strong anti-inflammatory properties, and wonderful calming effects when inhaled. Further research has confirmed superior efficacy of essential oils for a broad range of physiological conditions.

The most promising use of essential oils is in the treatment of infectious illness. Most essential oils display antibacterial effects, some with strong antiviral properties as well. However, it takes a qualified practitioner with the significant knowledge to choose the right oil for each condition.

Beyond infectious illness, certain essential oils have strong anti-inflammatory properties, stimulate the regeneration of tissues, help cleanse and purify the body, and can reduce muscular and joint pain while increasing circulation. Essential oils can play a significant role in any natural health program – the important part is a proper education of the user.

*Portions of this page’s content are courtesy of Zena Morris, author at Aromatherapy Answers, a leading website on aromatherapy, massage, and essential oils.
*Portions of this page’s content are courtesy of Danny Siegenthaler, a doctor of traditional Chinese medicine, medical herbalist, and aromatherapist. Together with his wife Susan, they have created Wildcrafted Herbal Products, a natural skin care product company, sharing their 40 years of combined expertise.